1. Field of the Invention
The present invention relates to an antenna for a mobile communication terminal, and, more particularly, to a dual radiating type inner antenna, which is provided within a case, for a mobile communication terminal.
2. Description of the Related Art
In general, an antenna is provided in a mobile communication terminal to transmit and receive electric waves. A conventional antenna protrudes to a predetermined height from an upper end of a mobile communication terminal case.
However, because a protruding antenna easily comes in contact with other objects, it is somewhat inconvenient to carry the mobile communication terminal. Particularly, the protruding antenna is easily damaged by external impact.
In order to solve such a problem, a mobile communication terminal was introduced in which an antenna is provided within a case. The inner antenna is also called an “intenna”.
FIG. 1 is a perspective view schematically illustrating a conventional inner antenna 100 for a mobile communication terminal. FIG. 2 is a cross-sectional view of the inner antenna taken along line II-II of FIG. 1.
Referring to FIGS. 1 and 2, the conventional inner antenna 100 includes a radiation plate 20 connected through a power supply unit 30 to an upper surface of a printed circuit board (PCB) 10 that is provided within a case 40. The PCB 10 has a structure in which a power supply pad 13 is formed in an upper surface and a ground layer 16 is formed in a lower surface of an insulating board body 12. The power supply unit 30 is bonded to the power supply pad 13.
The conventional inner antenna 100 radiates electromagnetic waves 50 of a predetermined frequency band through the radiation plate 20 when a current is supplied to the power supply unit 30 through the power supply pad 13. Because the lower surface of the PCB 10 under the radiation plate 20 is covered with the ground layer 16, the electromagnetic waves 50 are only radiated to an upper part of the radiation plate 20.
Because the conventional inner antenna 100 radiates electromagnetic waves 50 in only one direction through the radiation plate 20, a frequency bandwidth of the radiated electromagnetic waves 50 is limited, so that the inner antenna 100 is unable to function in an expanded frequency bandwidth.
When a mobile communication terminal is used for telephone communication, a user generally uses the terminal by holding the case 40 with one hand and bringing the terminal close to the user's head, whereby a frequency shift due to an effect of the human body may be generated. However, because the frequency bandwidth of the inner antenna 100 is limited, the shifted frequency may deviate from the frequency bandwidth of the inner antenna 100. In this case, the mobile communication terminal may not properly perform due to deterioration of the inner antenna performance.